Preparation of O,O-dialkyl-S-(N-methylcarboxamidomethyl)-thiolphosphoric acid esters

Abstract

A process for the preparation of an O,O-dialkyl-S-(N-methylcarboxamidomethyl)-thiolphosphoric acid ester of the formula ##STR1## in which R 1 and R 2 each independently is alkyl, comprising reacting a salt of N-methylcarboxamidomethyl-thiosulphuric acid with an O,O-dialkyl phosphorous acid of the formula ##STR2## in a suspension in the presence of an alkaline earth metal alcoholate, alkali metal carbonate or alkaline earth metal carbonate, e.g. magnesium methylate or ethylate, calcium methylate or ethylate, potassium carbonate, sodium carbonate, magnesium carbonate or calcium carbonate. Advantageously R 1 and R 2 each independently has up to 4 carbon atoms, the N-methylcarboxamidomethyl-thiosulphuric acid salt is an alkali metal salt and the reaction is carried out in ethylene chloride or chloroform at a temperature of about 10° to 40° C. in the presence of triethylamine as catalyst.

What is claimed is: 
     
       1. A process for the preparation of an O,O-dialkyl-S-(N-methyl-carboxamidomethyl)-thiolphosphoric acid ester of the formula ##STR9## in which R 1  and R 2  each independently is alkyl, comprising reacting a salt of N-methylcarboxamidomethyl-thiosulphuric acid with an O,O-dialkyl phosphorous acid of the formula ##STR10##  in a suspension in a non-polar solvent in the presence of an alkali metal carbonate or alkaline earth metal carbonate. 
     
     
       2. A process according to claim 1, in which the reaction is carried out in the presence of a nitrogen-containing organic base as a catalyst. 
     
     
       3. A process according to claim 2, in which the nitrogen-containing base is triethylamine. 
     
     
       4. A process according to claim 1, in which a chlorinated hydrocarbon is used as the non-polar solvent or diluent. 
     
     
       5. A process according to claim 4, in which the chlorinated hydrocarbon is ethylene chloride or chloroform. 
     
     
       6. A process according to claim 1, in which the reaction is carried out in the presence of potassium carbonate, sodium carbonate, magnesium carbonate or calcium carbonate. 
     
     
       7. A process according to claim 1, in which the reaction is effected at about 0° to +80° C. 
     
     
       8. A process according to claim 6, in which R 1  and R 2  each independently has up to 4 carbon atoms, the N-methylcarboxamidomethyl-thiosulphuric acid salt is an alkali metal salt, and the reaction is carried out in ethylene chloride or chloroform at a temperature of about 10° to 40° C. in the presence of triethylamine as catalyst. 
     
     
       9. A process according to claim 8, in which the salt of N-methylcarboxamidomethyl-thiosulphuric acid and the O,O-dialkyl phosphorous acid are first combined in ethylene chloride or chloroform and the carbonate is thereafter added.